1. Field of the Invention
The invention relates to a storage apparatus having a power usage control function, and a power usage control method in a storage apparatus.
2. Description of Related Art
Advancement of information society has brought about an enormous quantity of data, and storage apparatuses (storage subsystems) have further increasing their capacity accordingly. In order to deal with an increase in capacity of a storage apparatus, the addition of disk devices (hard disk drives) is promoted typically. The maximum power usage for the entire storage apparatus heavily depends on the number of hard disk drives disposed in the storage apparatus, and therefore, the addition of hard disk drives causes an increase in power consumption of the entire storage apparatus.
JP2000-293314 A discloses a storage system that controls power-saving operation (i.e., power-on/off and selection of a power-saving mode) after a predetermined time has passed since access from a host apparatus has stopped. Also, in the case of access from a host apparatus, if an access destination disk apparatus has been turned off, the storage system in JP2000-293314 A performs access after the disk apparatus is turned on.
JP2000-149383 A discloses a storage system that performs control so that a microprocessor in the storage system monitors the current power consumption during the operation of each group composed of disk devices; and when it is detected that the current power consumption increases to be equal to or more than a threshold value, the microprocessor cancels the operation of the disk devices to have the current power consumption remain equal to or less than the threshold value.
As described above, in order to deal with an increase in power consumption in a storage apparatus accompanied by an increase in storage capacity, the power consumption of the storage apparatus is controlled by suspending the power supply to a presently unnecessary disk device or canceling the operation of a disk device(s) if the power consumption exceeds a predetermined threshold value.
However, it may not be preferable that all the loaded hard disk drives are operated due to, for example, an environment where a storage apparatus is installed or a system administration policy. For example, when the maximum power usage for the storage apparatus exceeds the maximum allowable power for the floor on which the storage apparatus is installed, a breaker operates, which leads to unintended power disconnection.